A conventional hand truck for hauling luggage such as the one shown in FIG. 1 generally has a U-shape handle 1 of a selected height and a loading board 2 coupling to the bottom end of the handle 1. There are two wheels 3 coupled to the left and the right sides of the bottom ends of the handle 1. The lower sides of the U-shape handle 1 further are bridged by a transverse bracing bar 4. Luggage may be held on the loading board 2 and lean against the handle 1 and the bracing bar 4. However, such a structure cannot be folded in a smaller size on the front and rear sides when not in use. It takes too much floor space and is difficult to store.
To remedy this problem, a folding hand truck has been developed as shown in FIG. 2. It has a loading board 5 to couple with a wheel 6 through a gear seat 7 so that they may be driven simultaneously and folded on two sides of a frame 8. While it may save space for storing when not in use, it does not have any means to prevent the folded hand truck from breaking loose. The loading board 5 or the wheel 6 of the loosening hand truck could extend outwards and hurt people walking around. It has safety concern that needs be improved.